What measure involving steam lines is suggested to prevent water hammer?

• A. Warm system steam lines prior to initiating flow.
• B. Cool system steam lines prior to initiating flow.
• C. Vent steam lines continuously during startup.
• D. Ignore steam line temperature during startup.

Answer: (A)

Warming the steam lines before starting flow helps prevent water hammer by reducing rapid condensation and the formation of liquid slugs inside the pipe. When steam encounters cold piping, it condenses quickly, which can create a sudden surge of liquid water that is driven along the line as a pressure wave—the hammer. Pre-warming keeps the lines near steam temperature, so condensation happens more gradually and any condensate moves smoothly rather than forming a destructive slug. Cooling the lines would do the opposite, increasing condensation and hammer risk; venting continuously doesn’t address the initial condensation surge; ignoring temperature is unsafe.